.github: Use ASTERISKTEAM_PAT for PR merging

(cherry picked from commit 17c3080945)

.github/workflows/OnPRMergeApproved.yml

@@ -13,5 +13,7 @@ jobs:
     name: MergePR
     if: contains(fromJSON(vars.MERGE_APPROVED_LABELS), github.event.label.name)
     uses: asterisk/asterisk-ci-actions/.github/workflows/AsteriskMergePR.yml@main
+# Merging requires a specific token or it'll get caught in the rules that
+# prevent merges by mortals.
     secrets:
-      TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      TOKEN: ${{ secrets.ASTERISKTEAM_PAT }}